Apparatus and method for treatment of an intervertebral disc

ABSTRACT

A system and method for approaching the intervertebral disc through a percutaneous insertion from the back of a patient for thermal or electromagnetic treatment of an intervertebral disc, includes an elongated probe member having a guidable region adjacent its distal end with an undulating groove defined in its outer surface. The undulating groove is dimensioned to facilitate bending of the guidable region in at least one radial direction of movement relative to a longitudinal axis of the thermal probe. Preferably, the guidable region includes a plurality of undulating grooves, whereby adjacent undulating grooves are longitudinally spaced with respect to each other. The undulating grooves each define a sinusoidal configuration which may be arranged about an undulating axis extending in oblique relation to the longitudinal axis. The guidable region also includes a longitudinally extending backbone which resists bending of the guidable region in a radial direction of movement. The apparatus may also include a cannula to facilitate introduction of the thermal probe into the intervertebral disc. The cannula includes an arcuate end portion dimensioned to arrange the guidable region of the thermal probe at a desired orientation within the annulus fibrosis.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 10/439,881 filed on May16, 2003, now U.S. Pat. No. 6,980,862 which is a continuation of appl.Ser. No. 09/948,409 filed Sep. 6, 2001, now U.S. Pat. No. 6,604,003,which is related to and claims priority to U.S. Provisional ApplicationSer. No. 60/230,750 filed on Sep. 7, 2000. The disclosure of theseapplications and patent are hereby incorporated by reference in theirentirety.

BACKGROUND

1. Field of the Invention

The present invention relates generally to advances in medical systemsand procedures for prolonging and improving human life. Moreparticularly, this invention relates to a method and apparatus forthermally treating the intervertebral disc to relieve pain associatedwith abnormalities of the disc due to pathology of the disc orinterruption of the various neural processes in and around the disc.

2. Description of the Related Art

The use of radiofrequency electrodes for ablation of tissue in the bodyor for the treatment of pain is known. In a typical application, aradiofrequency probe or a resistive heating probe may be constructed inan elongated, cylindrical configuration and inserted into the body to atarget tissue which is to be treated or ablated. In the case of aradiofrequency probe, there may be an exposed conductive tip portion andan insulated portion of the probe. When connected to an external sourceof radiofrequency power, heating of tissue occurs near the exposedconductive portion of the probe, whereby therapeutic changes in thetarget tissue near the conductive tip are created by the elevation oftemperature of the tissue. Thermal probes can also be made by resistiveheating of a portion of the probe so as to heat surrounding tissue bythermal conduction. By reference, the products of Radionics, Inc.,located in Burlington, Mass., include commercially availableradiofrequency generators and electrode systems of variedconfigurations. A paper by Cosman, et al, entitled “Theoretical Aspectsof Radiofrequency Lesions in the Dorsal Root Entry Zone”, Neurosurgery,December 1984, Vol. 15, No. 6, pp. 945-950, describes aspects of tissueheating using radiofrequency electrodes and probes.

The use of thermal therapy in and around the spinal column is alsoknown. Heating of an intervertebral disc to relieve pain is described incommonly assigned U.S. Pat. No. 5,433,739 entitled “Method and Apparatusfor Heating an Intervertebral Disc for Relief of Back Pain” and incommonly assigned U.S. Pat. No. 5,571,147 entitled “Thermal Dennervationof an Intervertebral Disc for Relief of Back Pain”, the contents of eachpatent being incorporated herein by reference. In these patents,electrodes are described for either radiofrequency or resistive thermalheating of all or a portion of the intervertebral disc. Straight,curved, and flexible-tipped electrodes are described for this purpose.

U.S. Pat. No. 6,007,570 to Sharkey/Oratec Interventions discloses anintervertebral disc apparatus for treatment of the disc. The apparatusincludes a catheter having a self-navigating intradiscal section in theform of a conventional helical coil. In use, the intradiscal section isadvanced through the nucleus pulposus and is manipulated to navigatewithin the nucleus along the inner wall of the annulus fibrosis. Anenergy delivering member incorporated into the apparatus adjacent theintradiscal section supplies energy to treat the disc area.

The apparatus disclosed in Sharkey '570 is subject to severaldisadvantages which detract from its usefulness in relieving painassociated with an intervertebral disc. For example, navigation of thehelical coil of the catheter within the nucleus pulposus requires thesupport structure to wrap around in an approximately circular fashionfrom the anterior portion to the posterior portion of the intervertebraldisc. This serpentinus path of the support structure is difficult forthe surgeon to effectuate. Moreover, the configuration of the helicalsupport structure increases the risk of probe kinking and is deficientin consistently facilitating the prescribed movement within the disc.

It is desirable to treat the posterior or posterior/lateral portion ofthe intervertebral disc for the indication of mechanical degeneration ofthe disc and discogenic back pain. Pain can be derived from degenerationor compression of the intervertebral disc in its posterior orposterior/lateral portions. There is some innervation of theintervertebral disc near the surface of the disc and also within itsouter portion known as the annulus fibrosis. Mechanical damage such asfissures or cracks within the disc caused by age or mechanical traumamay result in disc innervation which is believed to be associated withpainful symptoms.

Accordingly, the present invention is directed to a novel apparatus andmethod of use which provides for direct and confirmable placement of athermal or electromagnetic field (EMF) treating element within theposterior/lateral and posterior portions of an intervertebral disc forthermal treatment. The apparatus includes a percutaneously introducablethermal application device having a novel configuration which providesexcellent torque transmission and an increased flexure in a specificdirection thereby facilitating the advancement of the thermal devicewithin an intervertebral disc and preferably, for example, in theannulus fibrosus between layers of annular tissue.

SUMMARY

The present invention is a novel and improved system and method forapproaching the intervertebral disc through a percutaneous insertionfrom the back of a patient. In one embodiment, the surgical apparatusincludes an elongated thermal or electromagnetic field creating probemember having a guidable region adjacent its distal end with anundulating groove defined in its outer surface. The undulating groove isdimensioned to facilitate bending of the guidable region in at least oneradial direction preferably, opposed radial directions, of movementrelative to a longitudinal axis of the thermal probe. Preferably, theguidable region includes a plurality of undulating grooves, wherebyadjacent undulating grooves are longitudinally spaced with respect toeach other. The undulating grooves each define a sinusoidalconfiguration which may be arranged about an undulating axis extendingin oblique relation to the longitudinal axis. The guidable regionincludes a longitudinally extending backbone which facilitates thedesired bending of the guidable region.

The apparatus may also include a cannula to facilitate introduction ofthe thermal probe into the intervertebral disc. The cannula defines alumen to receive the thermal probe with the thermal probe beingadvanceable within the lumen. The cannula includes an arcuate endportion dimensioned to arrange the guidable region of the thermal probeat a desired orientation within the intervertebral disc at a targetregion, for example, within the annulus fibrosis. The cannula may definea penetrating distal end dimensioned to penetrate the intervertebraldisc. Impedance measuring means are associated with the cannula tomonitor the impedance of tissue adjacent a distal end of the cannula toprovide an indication relating to tissue condition or type.

A preferred method for relieving pain associated with an intervertebraldisc having a disc nucleus pulposus and an outer annulus fibrosissurrounding the nucleus pulposus is also disclosed. The method includesthe steps of introducing a thermal or electromagnetic field (EMF)transmitting element of a probe into the annulus fibrosis of theintervertebral disc and supplying thermal or EMF energy from anappropriate source to the transmitting element to heat the annulusfibrosis adjacent the transmitting element sufficiently to relieve painassociated with the intervertebral disc.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the apparatus and method of the present invention willbecome more readily apparent and may be better understood by referringto the following detailed descriptions of illustrative embodiments ofthe present disclosure, taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 illustrates the apparatus in accordance with the presentinvention inserted percutaneously into the annulus fibrosis of anintervertebral disc;

FIG. 1A is a view illustrating an alternate use of the apparatus of FIG.1;

FIG. 2 is a schematic view of the apparatus in a disassembled conditionillustrating an insertion cannula, a thermal or EMF probe and associatedauxiliary electronic components;

FIG. 3 is a perspective view of the thermal probe of the apparatus;

FIGS. 4A and 4B are enlarged views of the guidable region of the thermalor EMF probe illustrating the undulating cuts to facilitate bendingmovement of the guidable region in a predetermined direction;

FIG. 5 is a side cross-sectional view of the guidable region of the EMFprobe;

FIG. 6 is a cross-sectional view of the guidable region taken along thelines 6-6 of FIG. 3;

FIG. 7 is a perspective view illustrating the pre-bend configuration ofthe guidable region of the EMF probe;

FIG. 8 is a side plan view of the proximal end of the EMF probeillustrating auxiliary electrical components associated with the probe;

FIG. 9 is a side cross-sectional view of the handle and associatedelectrical connections of the probe;

FIG. 10 is a cross-sectional view of the handle further illustrating ofrespective electrical components of the probe;

FIG. 11 is a cross-sectional view similar to the view of FIG. 6 andillustrating an alternate embodiment of the EMF probe;

FIG. 12 is a perspective view of a guidable region of another alternateembodiment of the thermal or EMF probe; and

FIG. 13 is a side view of the guidable region of another alternateembodiment of a thermal or EMF probe according to the presentdisclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus of the present disclosure provides a more precisecontrolled positioning of a thermal probe in an intervertebral disctargeted for treatment. It will be readily apparent to a person skilledin the art that the apparatus and method of use of the apparatus can beused to treat/destroy body tissues in any body cavity or tissuelocations that are accessible by percutaneous or endoscopic catheters oropen surgical techniques, and is not limited to the disc area.Application of the device and method in all of these organs and tissuesare intended to be included within the scope of this invention.

In the drawings and the following description, the term “proximal”, asis traditional, will refer to the end of the apparatus, or componentthereof, which is closest to the operator, and the term “distal” willrefer to the end of the apparatus, or component thereof, which is moreremote from the operator.

Referring now to FIG. 1, the apparatus of the present disclosure isshown positioned within an intervertebral disc. Prior to a detaileddiscussion of the apparatus, a brief overview of the anatomy of theintervertebral disc is presented. The intervertebral disc “D” iscomprised of an annulus fibrosis “A” and a nucleus pulposus “N” disposedwithin the annulus fibrosis “A”. The annulus fibrosis “A” consists of atough fibrous material which is arranged to define a plurality ofannular cartilaginous rings “R” forming the natural striata of theannulus. The nucleus pulposus “N” consists primarily of an amorphous gelhaving a softer consistency than the annulus “A”. The nucleus pulposus“N” usually contains 70%-90% water by weight and mechanically functionssimilar to an incompressible hydrostatic material. The juncture ortransition area of the annulus fibrosis “A” and nucleus pulposus “N”generally defines, for discussion purposes, an inner wall “W” of theannulus fibrosis “A”. The disc cortex “C” surrounds the annulus fibrosis“A”. The posterior, anterior and lateral aspects of the intervertebraldisc are identified as “P”, “AN” and “L”, respectively, with the opposedposterior-lateral aspects identified as “PL”.

When mechanical stress is put upon a disc or when a disc degenerateswith age, fissures, illustrated by the cracks “F” in the drawings, mayoccur in the posterior or posterior/lateral portions of the disc “D”.Problems with the nerves, fissures “F” and degenerative discs can giverise to various patient problems, such as back or leg pain originatingfrom the irritation or occurrence of these abnormalities. Moreover,these conditions may ultimately result in conditions such as bulging orherniated discs. Applicants have realized that heating and/orelectromagnetic field (EMF) therapy of the intervertebral disc,preferably, the annulus “A” in the posterior “P” or posterior-lateral“PL” portions, will result in denervation of nerves and/or alterationsand thermal ablation of disc structures, which will in turn producealleviation of pain and healing of the disc. Thus, it is desirable, asshown in FIG. 1, to have a practical method of placing a thermal orelectromagnetic probe in the posterior “P” and/or posterior-lateral “PL”portion of a disc “D” where these neural and aberrant structures occurfor the relief of pain and other disc related problems.

The apparatus of the present invention will now be described. Referringnow to FIGS. 1 and 2, apparatus 100 includes outer insertion orintroducer cannula 102, thermal or EMF probe 104 which is positionablewithin the cannula 102 and power source 106 which is connected to thethermal probe 102. Introducer cannula 102 preferably includes a rigidtubular shaft 108 defining a longitudinal axis “a” and having a rigidcurved or arcuate portion 110 adjacent its distal end, angularly offsetwith respect to the longitudinal axis “a” at an angle ranging from about15 to about 45.degree., preferably, about 23.degree. Shaft 108 ispreferably composed of a conductive material such as stainless steel orother suitable composition and is insulated with insulation along mostof its length as indicated by the hatching in FIGS. 1 and 2.Alternatively, shaft 108 may be fabricated from a suitable polymericmaterial and formed by conventional injection molding techniques. Thedistal end portion 112 of shaft 108 may be left uninsulated or exposedto permit electrical connection (e.g., for impedance measuring, etc.) toor contact with the tissue as cannula 102 is placed in the tissue.Alternatively, exposed portion 112 may be connected to power source 106to heat stimulate or micro-thermal generate the tissue to facilitatepassage through the tissue. The extreme distal tip 114 of shaft 108 ispreferably sharpened to facilitate penetration into the disc tissue,i.e., through the bone of the cortex “C” and into the annulus “A”. Ahandle or housing 116 is connected to the proximal end of cannula shaft108 to facilitate manipulation of cannula 102. Handle 116 may include anindex marker 118 to indicate the direction of arcuate portion 110 ofcannula 102 such that when thermal or EMF probe 104 is introduced withincannula 102, the surgeon may determine in which azimuthal rotationaldirection the curve is oriented. By reference, exemplary electrodeshafts and insulation materials are illustrated by the electrodesmanufactured by Radionics, Inc., Burlington, Mass.

Cannula shaft 108 may have a diameter ranging from a fraction of amillimeter to several millimeters and a length of a few centimeters upto about 20 centimeters or more. Alternatively, cannula shaft 108 may befabricated from an MRI compatible material, including cobalt alloys,titanium, copper, nitinol, etc. Arcuate portion 110 of cannula 102 mayassume a variety of angular orientations depending on the surgicalprocedure to be performed. In one preferred embodiment for thermal orEMF therapy of the intervertebral disc, arcuate portion 110 is arrangedsuch that thermal or EMF probe 104 is generally delivered from cannula102 in orthogonal relation to longitudinal axis “a”.

Power source or generator 106 may be, for example, a radio frequencygenerator providing energy at frequencies between several kilohertz toseveral hundred megahertz. An example of a suitable generator is thelesion generator, Model RFG-3C, available from Radionics, Inc.,Burlington, Mass. Power source 106 may have a power output ranging fromseveral watts to several hundred watts, depending on clinical need.Power source 106 may have control devices to increase or modulate poweroutput as well as readout and display devices to monitor energyparameters such as voltage, current, power, frequency, temperatureimpedance 109, etc., as appreciated by one skilled in the art. Othertypes of power sources are also contemplated, e.g., including resistiveheating units, laser sources, or microwave generators.

Referring now to FIGS. 3-6, in conjunction with FIGS. 1 and 2, thermalor EMF probe 104 of apparatus 100 will be discussed. Thermal or EMFprobe 104 is positionable within cannula 102 and is adapted forreciprocal longitudinal movement therewithin. Preferably, EMF probe 104is a monopolar system and is used in conjunction with an extendedsurface area grounding pad which contacts the patient's skin over a verylarge surface area relative the exposed surface area of the electrodetip. Thermal or EMF probe 104 includes handle 120 and elongated member122 extending distally from the handle 120. Handle 120 is advantageouslydimensioned for gripping engagement by the user and may be fabricatedfrom a suitable polymeric material or compatible metal. Handle 120houses the necessary electrical connectors for connecting to theexternal power source sensors, etc. Handle 120 may have a visualindicator, e.g., defining a flattened surface 121, to indicate thedirection of the elongated member 122. Elongated member 122 defines alongitudinal axis “e” as best illustrated in FIG. 4B, and has anexterior wall 124 defining axial bore or lumen 126, (FIG. 5), extendingsubstantially along its length within the exterior wall. The exteriorwall 124 at the proximal end of elongated member 122 is solid orcontinuous. The distal end of the elongated member includes guidableregion 128.

As best depicted in the enlarged plan views of a portion of guidableregion 128 of FIGS. 4A and 4B and the cross-sectional view of FIG. 5,guidable region 128 has a plurality of interrupted undulating grooves130 defined in exterior wall 124 and spaced along the longitudinal axis“e” of the probe 104. Grooves 130 preferably define a generallysinusoidal or “s” configuration having a waveform arranged to oscillateabout an axis “o” (FIG. 4B) extending in oblique relation to the axis“e” of the probe 104. Grooves 130 extend about the circumference ofguidable region 128 and preferably extend radially inwardly tocommunicate with internal lumen 126 of probe 104 (FIGS. 5 and 6),although, it is envisioned that grooves 130 may terminate within theexterior wall 124 of probe 104 without communicating with the internallumen 126.

Grooves 130 extend through a radial arc of approximately about270.degree. to about 350.degree. with respect to the longitudinal axis“e”. Grooves 130 are interrupted by backbone 132 (FIG. 4B) which extendsthe length of guidable region 128. In a preferred method of manufacture,each groove 130 is cut within the exterior wall 124 a predetermineddistance to leave a solid portion between the ends of the cuts therebyforming the single backbone 132. Backbone 132 is dimensioned to resistradial arcing movement of guidable region 128 toward the backbone whilepermitting guidable region 128 to move in radial directions “A, B”(FIGS. 6 and 7) across the backbone 132. Such feature providessignificant advantages during positioning of guidable region 128 withinthe intervertebral disc, including ease of control and guidance intopredetermined locations within the disc annulus “a”. More specifically,the undulating groove arrangement of guidable region 128 permits theregion 128 to bend or flex in opposed radial directions “A” and “B”along one radial plane to follow the ring like configuration of thenatural striata of the annulus fibrosis “A” while also providingexcellent torque transmission. The undulating groove arrangement alsoprovides a more streamline profile which, consequently, facilitatespassage of the probe 104 through the annular tissue, as compared toconventional helical coil arrangements which are subject to “catching”tissue during passage. As depicted in FIG. 7, guidable region 128 mayhave a preset bend at an angle ranging from about 15.degree. to about45.degree., preferably, about 30.degree. relative to the longitudinalaxis “e” of the probe 104. A preset bend facilitates introduction of theprobe 104 through the curved cannula into the annular tissue “A” toassist in initial guiding of the probe as it exits the cannula along thecurved path between annulus tissue layers. Preferably, flattened surface121 of handle 120 is aligned with the bend to indicate to the user theorientation of guidable region 128.

As will be appreciated, backbone 132 also serves as a more directelectrical pathway from the energy source to the distal end portion ofprobe 104 and, therefore, advantageously reduces the electricalresistance of guidable region 128 thereby facilitating uniform lesionformation along the length of the exposed electrode tip. The distal tip134 of guidable region 128 is preferably blunt or rounded to preventundesired entry or penetration of thermal probe into areas, includingunderlying nerves, the nucleus pulposus, etc., as will be discussed. Theproximal end of thermal or EMF probe 104 includes a plurality ofetchings or markings 136 (FIG. 2). Markings 136 indicate the degree ofextension of guidable region 128 from cannula 102.

When used as a radiofrequency probe, thermal or EMF probe 104 may beinsulated except for guidable region 128 which may be left uninsulatedfor transmission of energy. Alternately, and in the preferredembodiment, thermal or EMF probe 104 may be uninsulated while cannula102 functions as the insulating element of the apparatus. In thisarrangement, the degree of extension of guidable region 128 beyondcannula 102 determines the heating capability of the probe 104.

With reference to FIGS. 5-6, thermal or EMF probe 104 may furtherinclude a thermal sensor 138, e.g., a thermocouple, thermistor, etc.,extending through its internal lumen 126. Sensor 138 is preferablyembedded in solder tip 139 which also closes the distal tip 134 of probe104. Thermal sensor 138 provides temperature monitoring capability ofthe tissue being treated adjacent thermal or EMF probe 104 throughtemperature monitor 109 (FIGS. 1 and 6).

Referring particularly to FIGS. 3, 5 and 6, thermal or EMF probe 104further includes a guide wire 140. Guide wire 140 is disposed withininternal lumen 128 of thermal or EMF probe 104. Guide wire 140 hassufficient rigidity to assist in advancing thermal or EMF probe 104 withannulus “A” while also permitting guidable region 128 of the probe 104to flex and bend to conform to the path defined by the natural striataof the fibrous annulus tissue. Guide wire 140 is also embedded in soldertip 139 at the distal end of probe 104. In a preferred arrangement,thermosensor 138 is wrapped about the distal end of guide wire 140 andembedded in the solder tip 139.

With reference to FIGS. 8-10, in view of FIG. 5, guide wire 140 servesto carry electrical signals with elongated member 122 of probe 104 tothe distal end of the probe 104. Specifically, guide wire 140 andelongated member 122 are electrically connected to each other at theirrespective proximal ends through wire 143 (e.g. a #26 BUSS wire) whichis soldered to the proximal end of the elongated member 122. Wire 143and guide wire 140 are connected to an RF energy input pin 145 of handle102. (shown schematically in FIG. 8). This construction providesparallel dual pathways for the RF energy: 1) through elongated tubularmember 122 of probe 104 originating from the proximal end thereof andtraveling distally; and 2) through guide wire 140 to the distal end 134of probe 104. This dual path structure energy transmission provides asignificant advantage in that it facilitates a more uniform applicationof RF energy along the entire length of the exposed distal end of EMFprobe 104. The remaining connectors of handle 102 include pins 138 a,138 b for connection to respective constantan and copper wires of thethermocouple 138.

In an alternative embodiment, only elongated member 122 is connected tothe RF energy input with the guide wire 140 being electrically isolatedfrom the tube.

As depicted in the cross-sectional views of FIGS. 5 and 6, thermal orEMF probe 104 may further include flexible sleeve 142 which enclosesthermal sensor 138 and guide wire 140. Sleeve 142 serves to maintain thealignment of thermal sensor 138 and guide wire 140 within thermal or EMFprobe 104 and also prevents or minimizes entry of body fluids within theprobe 104. Sleeve 142 preferably comprises a flexible polymer material,such as polyimide.

With reference again to FIGS. 1 and 2, the remaining components of theapparatus will be discussed. Apparatus 100 preferably includes animaging system 144 to potentially monitor, control or verify thepositioning of cannula 102 and/or thermal probe 104. Imaging systemscontemplated include X-ray machines, fluoroscopic machines or anultrasonic, CT, MRI, PET, or other imaging devices. Several of thesedevices have conjugate elements as illustrated by element 146 on theopposite portion of the patient's body to provide imaging data. Forexample, if the imaging machine is an X-ray machine, element 146 may bea detection device, such as an X-ray film, digital, X-ray detector,fluoroscopic device, etc. Use of imaging machines to monitorpercutaneously placed electrodes into tissue is commonly practiced inthe surgical field.

With continued reference to FIG. 2, in conjunction with FIG. 1,apparatus 100 may further include stylet 148 which is to be used inconjunction with cannula 102. Stylet 148 is positionable within thelumen of cannula 102 and preferably occludes the front opening of thecannula 102 to prevent entry of tissue, fluids, etc., duringintroduction of the cannula 102 within the intervertebral disc “D”.Stylet 148 may include a proximally positioned hub 150 which mates withhandle 116 of cannula 102 to lock the components together duringinsertion. Such locking mechanisms are appreciated by one skilled in theart. An impedance monitor 152 can be connected, as shown by connection154, to stylet 148 and therefore communicates electrically with theexposed portion 112 of cannula 102 into which the stylet 148 isintroduced to monitor impedance of the tissue adjacent the distal end ofcannula 102. Alternatively, connection of the impedance monitor may bemade directly to the shaft of cannula 102 whereby impedance measurementsare effectuated through the exposed distal end of the cannula 102. Oncethe combination of stylet 148 and cannula 102 are inserted into thebody, impedance monitoring assists in determining the position ofcannula tip 112 with respect to the patient's skin, the cortex “C” ofthe disc, the annulus “A”, and/or nucleus “NU” of the disc “ID”. Theseregions will have different impedance levels that are readilyquantifiable. For example, for a fully insulated electrode or cannulawith an exposed area of a few square millimeters at the cannula end, theimpedance will change significantly from the position of the tip near toor contacting the cortex “C” of the disc to the region where the tip iswithin the annulus “A” of FIG. 1 and further where the tip is within thenucleus “NU” of the disc. Differences of impedance can range from a fewhundred ohms outside the disc, to 200 to 300 ohms in the annulus, toapproximately 100 to 200 ohms in the nucleus. This variation can bedetected exquisitely by the surgeon by visualizing impedance on metersor by hearing an audio tone whose frequency is proportional toimpedance. Such a tone can be generated by monitor 109 in FIG. 2. Inthis way, an independent means is provided for detecting placement ofthe curved cannula within the disc. Thus, e.g., in an application wherethe EMF probe 104 is to be inserted between adjacent layers of annulartissue, undesired penetration of the EMF probe 104 tip portion 112 ofcannula 102 through the inner wall “W” of the annulus “A” and into thenucleus pulposus “N” can be detected via the impedance monitoring means.

Stylet 148 can be made of a rigid metal tubing with either a permanentbend 156 at its distal end to correspond to the curvature of arcuateportion 112 of cannula 102 or may be a straight guide wire to adapt tothe curve of the cannula 102 when it is inserted within the cannula 102.The hub 150 and connector 154 can take various forms including luerhubs, plug-in-jack-type connections, integral cables, etc. By reference,example of electrodes and cables are illustrated in the product lines ofRadionics, Inc., Burlington, Mass.

Surgical Procedure

The use of the apparatus 100 in accordance with a preferred procedurefor thermal treatment of an intervertebral disc will now be discussed.With reference to FIG. 1, the targeted intervertebral disc “D” isidentified during a pre-operative phase of the surgery. Access to theintervertebral disc area is then ascertained, preferably, throughpercutaneous techniques or, less desirably, open surgical techniques.Cannula 102 with stylet 148 positioned and secured therein is introducedwithin the intervertebral disc “D” preferably from a posterior orposterior-lateral location as depicted in FIG. 1. Alternatively, cannula102 may be utilized without stylet 148. During introduction of theassembled components, the impedance of the tissue adjacent the distalend 114 of the cannula 102 is monitored through the cannula 102 oralternatively via the impedance monitoring means associated with stylet148. Impedance monitoring may be utilized to determine the position ofcannula tip 114 with respect to the patient's skin, the cortex “C” ofthe disc, the annulus “A” and/or the nucleus “N” of the disc. Asdiscussed above, these regions have different and quantifiable impedancelevels thereby providing an indication to the user of the position ofthe cannula tip 112 in the tissue. Monitoring of the location of cannula102 may also be confirmed with imaging system 144. In a preferredprocedure, cannula tip 114 of cannula 102 is positioned within theannulus fibrosis “A” of the intervertebral disc “D” at a posteriorlateral “PL” location of the disc “D” without penetrating through innerwall “W” and into nucleus “N”. As appreciated, sharpened tip 114facilitates entry into the annulus “A”.

Thereafter, cannula 102 is angulated to position arcuate end portion 110of the cannula 102 at the desired orientation within the annulusfibrosis “A”. Confirmation of the angular orientation of arcuate endportion 110 of cannula 102 is made through location of index marker 118of the cannula 102. In one preferred orientation, arcuate end portion110 is arranged to deliver thermal probe 104 within the posteriorsection “P” of the intervertebral disc “D”. In an alternative procedure,arcuate end portion 110 is arranged to deliver thermal or EMF probe 104toward the posterior-lateral “PL” and lateral “L” portion of the disc“D” as shown in phantom in FIG. 1.

Stylet 148 is then removed from cannula 102. Thermal or EMF probe 104 ispositioned within the internal lumen of cannula 102 and advanced throughthe cannula 102. Preferably, the pre-bent orientation of guidable region128 is arranged to coincide with the arcuate end portion of the cannula102. Confirmation of this orientation may be made with the location ofthe flattened surface 121 of the handle 102. The probe 104 is advancedto at least partially expose guidable region 128 of the thermal or EMFprobe 104 from the distal end of cannula 102. As thermal or EMF probe104 enters the annulus fibrosis “A”, guidable region 128, due to itsstrategic configuration and undulating groove 130 arrangement, flexesand conforms to the natural striata of the annular rings “R” of theannulus fibrosis, i.e., follows a path defined by the natural striatabetween two adjacent annular layers of tissue without entering thenucleus “N”. Once positioned, guidable region 128 occupies a substantialportion of the posterior “P” section of the annulus fibrosis “A” andpreferably extends to the opposed posterior lateral section “PL” of theannulus fibrosis. The degree of extension of guidable region 128 beyondcannula 102 may be indicated by distance or index markings 136 on theshaft of thermal or EMF probe 104 and confirmed through imaging system144. In the alternate method shown in phantom in FIG. 1, arcuate endportion 110 is angulated to directly access the posterior lateral “PL”section of the annulus fibrosis “A” also without entering the nucleuspulposus. Thermal or EMF probe 104 is thereafter advanced to positionguidable region 128 within the lateral “L” and posterior/lateral “PL”sections of the annulus “A”. Similar to the predescribed method ofapplication, guidable region 128 follows the arcuate path of the naturalstriata of the annulus “A” upon advancement therein. In either method,confirmation of the orientation of arcuate end portion 110 is providedthrough index pin or marker adjacent handle of the cannula and can bealso monitored through imaging system 144.

In one alternative method of application depicted in FIG. 1A, cannula102 may be positioned adjacent inner wall “W” of annulus. As in thepreferred embodiment previously described, thermal or EMF probe 104 isadvanced within the annulus fibrosis “A” between adjacent layers,whereby guidable region 128 follows along the arcuate path defined bythe adjacent annular tissue layers without penetrating through the wall“W” and into the nucleus “N”.

Once the guidable region 128 is positioned within the annulus “A” asdesired, the power source 106 is activated whereby the thermal or EMFprobe 104 delivers thermal energy and/or creates an electromagneticfield through guidable region 128 adjacent the intervertebral disc “D”to produce the thermal and/or EMF therapy in accordance with the presentinvention. Appropriate amounts of power, current or thermal heat may bemonitored from the external power source 106 and delivered for a certainamount of time as determined appropriate for clinical needs. Forexample, if denervation of nerves surrounding the disc is the objective,the tissue adjacent the probe end is heated to a temperature of fromabout 45.degree. to about 60.degree. If healing of fissures in the discis the surgical objective, the temperature in the tissue is raised toabout 60-75.degree. C. As appreciated, the degree of extension ofguidable region 128 from cannula controls the volume of disc tissueheated by the probe 104. Thermal sensor 138 of thermal or EMF probe 104can provide information concerning the temperature of tissue adjacentthe distal end. The impedance means associated with e.g., EMF probe 104,can provide impedance measurements of the tissue thereby providing anindication of the degree of dessication, power rise, or charring, thatmay be taking place nea the thermal probe tip 134. This indicates theeffectiveness of the treatment and guards against unsafecontraindications of the therapy. By reference, use of impedancemonitoring in neurosurgery is described in the paper byh E. R. Cosmanand B. J. Cosman, entitled “Methods of Making Nervous Syustem Lesions”,in Neurosurgery, Vol. 3, pp. 2490-2499, McGraw Hill 1985.

Thus, the apparatus of the present invention provides significantadvantages over the prior art.

Cannula 102 and thermal or EMF probe 104 permits the probe to bedirected from a location across the posterior margin and into thelateral portion of the disc “D” by a direct pathway along, e.g., thenatural striata of the annulus fibrosis or along the inner wall “W” ofthe annulus fibrosis. This represents a more direct approach to theposterior/lateral portions of the disc than the more circuitous approachinvolving delivering a probe into the nucleus center of the disc andthen arcing the probe around through an anterior or anterior-lateralpathway through the nucleus “N”. Moreover, the present inventioneliminates the need of known devices to penetrate the inner annulus wall“W” and enter the nucleus “N” with a guide.

A further advantage of the present invention is that by monitoringimpedance of cannula 102 and/or thermal or EMF probe 104 as it is beingpositioned within the disc, the surgeon can get additional informationon the positioning of the cannula 102 as it is being put into the properorientation.

A further advantage of the present invention is that by use of a curvedintroduction cannula a more efficacious direction of the probe can beachieved in the difficult lumbar or lumbar-sacral intervertebral discs.In these approaches, nearby heavy bony structures, such as the iliaccrest, can often obscure a placement of a curved probe parallel to theend plates or bony margins of adjacent intervertebral discs. Byappropriate angulation and rotation of a curved cannula, the extensionof a thermal probe parallel to the so-called end plates of theintervertebral discs is made possible with minimal repositioning andmanipulation of the introduction cannula.

The undulating groove arrangement and backbone of the guidable region ofthe thermal probe permits flexing in at least opposed radial directionsalong one radial plane to follow the arcuate path in the intervertebraldisc. The undulating groove arrangement also provides a streamlineprofile thereby facilitating entry and passage through the annulustissue.

In typical radiofrequency procedures using the apparatus and process ofthe present invention, power levels of fractions of a watt to severaltens of watts may be used depending on the extent of heating requiredand the degree of therapy, denervation, and disc healing that is desiredto be achieved.

A further advantage of the present system and method is that it enablessimple, minimally-invasive, percutaneous, out-patient treatment ofintradiscal pain without the need for open surgery as for examplediscectomies or spinal stabilization using plates, screws, and otherinstrumentation hardware. A further advantage of the present inventionis that it is simple to use and relatively economical. Compared to opensurgery, the treatment of disc by percutaneous electrode placementrepresents only a few hours procedure and minimal hospitalization, withminimal morbidity to the patient. Open surgical procedures often requirefull anesthetic, extensive operating room time, and long hospital andhome convalescence. Such open surgeries have considerable risk ofmorbidity and mortality and are much more expensive than a percutaneousprocedure as described in accordance with the present invention.

It is also envisioned that thermal or EMF probe could be, orincorporate, a resistive heating element(s) to heat the disc tissue byresistive heating. For example, within the distal end there may be aresistive wire such as a nichrome wire or other type of resistiveelement, such that current delivered to the resistive element from thepower generator will produce resistive heating within the element. Suchheating of the proximate disc material when the electrode is insertedinto the disc of a patient. Various construction details for suchresistive heating elements can be devised by those skilled in the art.For example, a resistive wire can be fabricated to produce the guidableregion. Alternatively, an internal resistive wire can be placed insidethe guidable region. The overall shaft may be coated with an insulativematerial or other material to produce appropriate frictional, thermal,or electrical characteristics of the electrode when it is placed in thedisc. Like the high frequency electrode embodiment, as described above,such a resistive element may have the appropriate flexibility, orsteering capability so that it can be steered or directed favorablywithin the appropriate portion of the posterior and posterior-lateralportions of a disc, as illustrated by the discussion associated withFIG. 1 above.

In another configuration of the thermal probe, in accordance with thepresent disclosure, the distal end may comprise a microwave antennasystem or a laser fiber with transducer to distribute energy throughthermal element into surrounding disc tissue. In the configuration shownin FIG. 1, the thermal transmitting element operates as a microwaveantenna or laser transmitting element, respectively. Other constructionsto produce a heating element can be devised by those skilled in the artand are intended to be included within the scope of the presentinvention. It is further envisioned that the thermal or EMF probeprovided with undulating cuts can be positioned such that thetransmitting guidable region is disposed within the nucleus “N”.

In such an embodiment, however, the probe must be configured anddimensioned so as to be more flexible than that of the previouslydisclosed embodiment. For example, the probe 104 may have a differentdiameter, thickness, material of fabrication and/or differentarrangement and orientation of the grooves 130. This is so because theprobe which is to be inserted into and navigated within the nuclearmaterial must have greater flexibility to prevent puncturing through theopposing side of the nucleus pulposus back into the annulus. Also, thegreater flexibility facilitates navigation of the probe along the innersurface of the nucleus. Whereas, in the previously described embodiment,the opposite is desirable. In particular, the probe of the previouslydescribed embodiment must be significantly more rigid to provideincreased columnar strength to prevent kinking of the probe caused bygreater relative resistance encountered by navigating in the annulartissue. The two embodiments would not, therefore, be interchangeable intheir methods of use, i.e., operating in the annular tissue as for thepreviously described embodiment and operating in the nuclear material asfor the embodiment of this paragraph.

Referring now to the cross-sectional view of FIG. 11, a furtheralternative embodiment of the probe of the present invention isdisclosed. This probe is substantially similar to the probe of the priorembodiment but, includes, a second backbone 132 in diametrical opposedrelation to the first backbone 132. Second backbone 132 is created byinterrupting the sinusoidal grooves 130 adjacent the area of the secondbackbone 132. This double backbone arrangement permits radial movementalong one plane in directions “A and “B”, but, also enhances rigidity ofthe guidable region, which may be desirable in certain surgicalapplications.

Referring now to FIG. 11, there is illustrated a further alternativeembodiment of the probe of the present invention. This probe is similarto the probe 104 of the first embodiment, but, includes a singlecontinuous sinusoidal groove 170 extending the length of the guidableregion 172. This configuration provides for uniform radial movement inall radial directions with respect to the longitudinal axis. Suchconfiguration may be advantageous when inserting probe along a moreserpenticious path. Groove 170 extends to communicate with the internallumen of the probe as discussed hereinabove.

Referring now to FIG. 12, there is illustrated another alternativeembodiment of thermal or EMF probe 104. Thermal or EMF probe 104includes a guidable region 200 having a plurality of partial annulargrooves 202 or cuts spaced along the longitudinal axis “Z”. FIG. 13 isan enlarged plan view of a portion of guidable region 200. In apreferred embodiment, annular grooves 202 radially extend about theexterior wall through an arc which is slightly less than 360.degree.,thereby providing a solid region 204, 206 between the respectivestarting and ending positions of the groove. Adjacent grooves 202 areradially displaced at about 180.degree. The overall effect of thisarrangement is that guidable region can flex uniformly in all radialdirections. This configuration is advantageous in insertion of the probealong a more serpenticious path.

While the above description contains many specific examples, thesespecifics should not be construed as limitations on the scope of thedisclosure, but merely as exemplifications of preferred embodimentsthereof. Those skilled in the art will envision many other possiblevariations that are within the scope and spirit of the disclosure asdefined by the claims appended hereto.

1. A surgical apparatus which treats tissue, comprising: an elongatedprobe member comprising a proximal end, a distal end, an outer wall anddefining a longitudinal axis, the elongated probe member comprising aninternal lumen and a guidable region adjacent the distal end, theguidable region comprising a plurality of undulating grooves whichdefine a non-linear path along the outer wall in communication with theinternal lumen and being dimensioned to facilitate bending of theguidable region in at least one of a plurality of radial directionsrelative to the longitudinal axis, the elongated probe member beingadapted for connection to a thermal energy source which provides thermalenergy to tissue; and a cannula which facilitates introduction of theelongated probe member into the intervertebral disc, the cannulacomprising a shaft comprising a proximal end and a distal end anddefining a lumen which receives the elongated probe member, theelongated probe member being advanceable within the lumen.
 2. Thesurgical apparatus according to claim 1, wherein the cannula comprisesan arcuate portion disposed adjacent the distal end, the arcuate portiondimensioned to arrange the guidable region of the elongated probe membertowards a desired orientation within the annulus fibrosis.
 3. Thesurgical apparatus according to claim 2, wherein the arcuate portion ofthe cannula is angularly offset with respect to the longitudinal axis atan angle between about 15° to about 45°.
 4. The surgical apparatusaccording to claim 2, wherein the arcuate portion of the cannula isangularly offset with respect to the longitudinal axis at an angle ofabout 23°.
 5. The surgical apparatus according to claim 1, wherein atleast a portion of the shaft of the cannula is made from a conductivematerial.
 6. The surgical apparatus according to claim 1, wherein atleast a portion of the shaft of the cannula is made from stainlesssteel.
 7. The surgical apparatus according to claim 1, wherein at leasta portion of the shaft of the cannula is made from a polymeric material.8. The surgical apparatus according to claim 1, wherein at least aportion of the cannula is insulated.
 9. The surgical apparatus accordingto claim 1, wherein the plurality of undulating grooves extend at leastpartially longitudinally from an originating point.
 10. The surgicalapparatus according to claim 9, wherein at least one of the plurality ofundulating grooves includes an origin and a terminus separated adistance from each other.
 11. The surgical apparatus according to claim10, wherein the origin and the terminus are substantially at the samelongitudinal position along the length of the guidable region.
 12. Thesurgical apparatus according to claim 1, wherein at least one of theundulating grooves defines a sinusoidal configuration.
 13. The surgicalapparatus according to claim 1, wherein the guidable region comprises alongitudinally extending backbone, the backbone being devoid of theundulating grooves and being dimensioned to resist bending of theguidable region in a radial direction of movement.
 14. The surgicalapparatus according to claim 1, further comprising an impedance monitorassociated with the cannula which monitors the impedance of tissueadjacent the distal end of the cannula which provides an indicationrelating to at least one of tissue condition and tissue type.
 15. Thesurgical apparatus according to claim 14, wherein the impedance monitorcomprises a stylet which is at least partially positionable within thelumen of the cannula.